Apparatus and method for producing an end of an optical fiber bundle and improved optical fiber bundle made with same

ABSTRACT

A method and apparatus are described, which permit a simple, rapid manufacture of an end of an optical fiber bundle. According to the method a metallic sleeve is placed on an end section of the bundle, the end section with the sleeve on it is positioned in a shaping tool without pressing the sleeve and then pressure is exerted on the sleeve exclusively in a radial direction by press jaws of the shaping tool. In the optical fiber bundle made by the method the outer optical fibers ( 4 ′) of the optical fiber bundle ( 1 ) are embedded at least partially in the sleeve material. The apparatus for making the end of the bundle ( 1 ) with the sleeve ( 10 ) has a shaping tool ( 20 ) including at least two radially movable press jaws ( 22   a - 22   f ) that substantially surround the sleeve ( 10 ).

CROSS-REFERENCE

This is a divisional, filed in accordance with 35 U.S.C. 120, of U.S.patent application, Ser. No. 11/143,900 filed Jun. 02, 2005 from whichU.S. Pat. No. 7,457,499 has issued.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of making or producing an endof an optical fiber bundle, in which a sleeve is placed or mounted ontoan end section of the optical fiber bundle and the sleeve is pressed ina shaping tool at least while exerting pressure on the end section. Thepresent invention also relates to an apparatus for making or producingthe end of the optical fiber bundle with the sleeve, which comprises aholder for holding the end section of the optical fiber bundle and ashaping or pressing tool, in which the sleeve can be pressed against theend section of the optical fiber bundle.

2. Related Art

Frequently a flexible light guide comprising a plurality of individualoptical fibers, a so-called optical fiber bundle, is used for lighttransmission. The individual optical fibers are usually fastenedtogether in a common end in a sleeve, which, for example, is fixed to alight source serving for illumination.

It is known to bond the individual optical fibers with each other byadhesive and with a sleeve that is pushed on them or alternatively bymelting the individual optical fibers together in the common sleeve.

JP 3144601 describes a method, with which the end of an optical fiberbundle can be provided. For this purpose the optical fiber bundle end isheated and inserted into a narrowing or constricting opening. Thediameter of the bundle is reduced in that way and the bundle iscompressed together.

DE 2 630 730 A1 describes a method that begins in the same manner. Inthis method the end of the optical fiber bundle is similarly insertedinto a metallic sleeve. The fiber optic bundle together with the sleeveis then pushed into a narrowing or constricting hole, which is providedin a pressing member. The end of the optical fiber bundle is shaped bymeans of the sleeve by moving the end of the fiber optic bundle equippedwith the sleeve in an axial direction while simultaneously heating.

DE 19 855 958 A1 similarly provides a method in which the terminalregion of an optical fiber bundle is equipped with a metallic sleeve andsubsequently held in a clamping apparatus. A shaping tool with adecreasing or narrowing inner diameter moves in an axial direction onthe sleeve and converts the fiber ends into a hexagonally packedarrangement by heat transfer. There is a gap between the inner wall ofthe shaping tool and the sleeve, in which the heat transfer to the endsof the optical fibers occurs by means of an annular section at the frontend of the optical fiber bundle. The conversion process is conducted sothat no glass seal is formed between the optical fiber bundle and themetallic sleeve.

This process has the disadvantage that an axial force must be exerted onthe optical fiber bundle when it is inserted in the sleeve, which canlead to damage at least to the outer optical fibers of the bundle.Furthermore the sleeve must have suitable stability, so that a materiallike steel must be selected for it or a large wall thickness isrequired.

In the methods described in DE 32 47 500 A1 and DE 37 44 367 C1 meltedglass is injected around a glass fiber bundle arranged in a sleeve bymeans of an annular injecting means. The apparatuses performing thesemethods are comparatively expensive.

According to GB 1 595 163 a thermoplastic terminal sleeve is bonded tothe thermoplastic protective jacket of the optical fiber bundle byultrasonic welding using a two part sonotrode and to the optical fiberbundle.

U.S. Pat. No. 3 914 015 describes a fiber binder. The end sleeveinserted in this fiber binder comprises a shrinkable metal, which isshrunk onto the fiber ends at a temperature of about 75° C.

U.S. Pat. No. 5 222 180 describes a process for making a terminatingmember for a fiber bundle made from polymer fibers. The fibers are drawncold, inserted in a sleeve and then heated. During heating they attemptto regain their original shape and fill the sleeve cross-section.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method, whichpermits rapid manufacture of an end of an optical fiber bundle in asimple manner.

It is a further object of the present invention to provide an apparatusfor performing the method for making the end of the optical fiberbundle, which includes a shaping or pressing tool.

It is also an object of the present invention to provide an improvedoptical fiber bundle of optical fibers made of glass, which has a sleeveon an end section of the bundle that has a clearly stronger seat on theoptical fiber bundle than in similar optical fiber bundles of the priorart.

The method of making or producing an end of an optical fiber bundlecomprises the steps of:

a) placing or mounting a sleeve on an end section of the optical fiberbundle, the optical fiber bundle comprising a plurality of opticalfibers made of glass;

b) inserting and positioning the end section of the optical fiber bundlewith the sleeve placed on the end section in a pressing tool withoutpressing on the sleeve, said pressing tool having more than two heatedpress jaws; and

c) after the inserting and positioning of step b), exerting pressure onthe sleeve exclusively in a radial direction by means of the press jaws.

The pressing process is simultaneously applied to the entire outersurface of the sleeve to be pressed. In contrast to an axial insertionof the pressing tool and a pressing process proceeding in the axialdirection, as in the case of the prior art, substantial time is saved.The pressing times were reduced from the minute range to the secondrange.

An additional advantage is that the outer optical fibers of the bundleare exposed to scarcely any axial load so that damage to these opticalfibers is avoided. Since the bending of the sleeve during processingbecause of axial forces is no longer feared, the sleeve material nolonger needs to have the stability required in the prior art. The sleevecan be made from a ductile material with reduced wall thickness.

Also deep-drawn sleeves of reasonably priced material, e.g. brass, canbe used in the method according to the invention, in contrast to thesleeves, which are usually machined or milled in the methods of theprior art.

Deep-drawn sleeves may be made with clearly reduced outer diameters thanthe milled parts so that optical fiber bundles with outer diameters inthe range of a few mm can also be provided with a terminal sleeve.

Since thin-walled sleeves can be used due to the missing axial load andthe resulting optical fiber bundle can have smaller dimensions, newareas of application have thus been opened up for the optical fiberbundle. The end of the optical fiber bundle can be integrated in currentplug connections of standard dimensions. Thus the end of the opticalfiber bundle can be used for plugs according to the MOST standard, whichare used in automobile applications. Also simpler sleeve geometries areusable, for example sleeves without annular collars, since the sleevedoes not need to be fixed in the axial direction.

Preferably the optical fibers of the end section are not pressedtogether during insertion in the sleeve. The fibers are of course heldfixed, but are not in a press fit. An axial load on the optical fibersis avoided when the sleeve is put on them.

The sleeve is preferably heated to 500° C. to 700° C., especially 550°C. to 650° C., during the making of the end of an optical fiber bundle,in which the optical fibers are made from glass and a metallic sleeve isused.

The pressing times are clearly shortened because the heating occurs atthe same time over the entire outer surface of the sleeve to be shaped.

The optical fiber bundle made by the method is characterized in that theouter optical fibers of the bundle are at least partially embedded inthe material of the sleeve.

Preferably the sleeve comprises a ductile material. Because of that thematerial of the sleeve is deformable during the working-in process, theouter optical fibers can be pressed into the material of the sleeve,whereby the optical fibers are interconnected with the sleeve material.A clearly more stable connection between the optical fibers and thesleeve is obtained, which is observable in larger pull-out forces.

In order to make this embedding possible during the method the sleevematerial must be softer and more plastic than the optical fibers. Thesleeve preferably comprises metal, especially brass, or glass.

The sleeve preferably has a wall thickness of 0.3 to 0.4 mm. This wallthickness is especially necessary with smaller outer diameters, whichare in a range of greater than or equal to 0.5 mm. The preferred outerdiameter of the sleeve can be 0.5 to 25 mm. A large range of opticalfiber bundle diameters is thus covered.

In the simplest embodiment the sleeve can be cylindrical and comprisesonly one pipe section.

Preferably only one section of the sleeve is pressed.

It is advantageous when the sleeve has a larger diameter sleeve sectionand a smaller diameter sleeve section prior to pressing, because thelarger diameter section can act as an aid for insertion of the opticalfiber bundle end.

The apparatus for making an end of the optical fiber bundle with asleeve has a shaping tool with more than two press jaws surrounding thesleeve that are movable in a radial direction in order to guarantee ascomplete a coverage on all sides of the sleeve as possible. Preferablythe shaping tool has six press jaws.

The term “radial direction” herein means a direction perpendicular tothe longitudinal axis of the sleeve.

Preferably a counter ring is provided, on which the press jaws engage,wherein preferably the outer surface of the press jaws taken togetherbears on the inner surface of the counter ring, and the counter ring andthe press jaws are movable in an axial direction relative to each other.

The “axial direction” herein means the direction of the longitudinalaxis of the sleeve, which is the same as the longitudinal axis of theshaping tool. The press jaws are movable inwardly in a radial directionduring the motion of the counter ring in relation to the press jaws.

The counter ring can have a conical interior surface, which slides overthe front edges of the press jaws or over the outer surface of the pressjaws.

Preferably each press jaw has a section narrowing or tapering to itsfree end.

The outer surface of all press jaws taken together can be in the shapeof a truncated pyramid or cone. Because of that a sliding surface, overwhich the interior surface of the counter ring can slide, is formed onthe press jaws.

In order to make the sliding easier and/or to reduce the wear of theparts, the inner surface of the counter ring and/or the outer surface ofthe press jaws can be provided with a heat-resistant sliding coating,especially comprising titanium or aluminum nitride.

Preferably the press jaws are spring-loaded or spring-biased in a radialdirection. It is of advantage when the press jaws are movable inwardlyin a radial direction against a spring force acting outwardly in theradial direction or radially. The press jaws move back into their openposition after the pressing process because of the spring force thatacts to move them outwardly.

Preferably the shaping tool comprises a pipe-shaped body, which has anend section provided with longitudinal slots or slits. The press jawscomprise the pipe segments separated by the longitudinal slits or slots.The pipe segments are arranged spring-loaded in this way in thepipe-shaped body.

The shaping tool has at least one heating unit. The heating unit cancomprise an induction heater, heating strip heating jacket and/orheating cartridge. Because of the high temperatures, which are requiredin pressing of the metallic sleeve, it is necessary that the shapingtool comprise a heat-resistant material.

In a preferred embodiment of the apparatus each press jaw is equippedwith its own heating cartridge.

The apparatus comprises a holder for holding the end section of theoptical fiber bundle.

Preferably the holder is movable in an axial direction. This movabilityis especially advantageous when the wear on the counter ring and/or theouter surface of the press jaws has proceeded so far that the axialmovement of the parts must be increased. Also tolerances of the sleevedimensions and dimensions of the optical fiber bundle end can becompensated by a larger shift between the counter ring and the pressingtool. An axially movable and if necessary spring-loaded positioning ofthe holder of the optical fiber bundle increases the axial forces sothat damage to the optical fibers car, be effectively avoided.

BRIEF DESCRIPTION OF THE DRAWING

The objects, features and advantages of the invention will now beillustrated in more detail with the aid of the following description ofthe preferred embodiments, with reference to the accompanying figures inwhich:

FIG. 1 is a cross-sectional view through an apparatus for making an endof an optical fiber bundle according to the invention;

FIG. 2 is a perspective view of a shaping or pressing tool;

FIG. 3 is a detailed perspective view of a front end of anotherembodiment of a shaping or pressing tool used in the apparatus accordingto the invention; and

FIG. 4 is a cutaway front plan view of a portion of the front surface ofthe optical fiber bundle with the pressed-on sleeve.

DESCRIPTION OF THE PREFERED EMBODIMENTS

An apparatus for making an end of an optical fiber bundle is shown inFIG. 1. An optical fiber bundle 1 with a protective sheathing 2 is shownon the left side of FIG. 1. This optical fiber bundle 1 has an endsection 3, which is free of the protective sheathing 2. A sleeve 10 ispushed over this end section 3 and the end section of the protectivesheathing 2. The sleeve 10 has a larger diameter section 12 and asmaller diameter section 13. A collar 11, which however has nosignificance for the inventive method and also can be omitted, is formedon the rear end of the larger diameter section 12. The sleeve 10 is heldin the vicinity of the larger diameter section 12 by a holder 40, whichis slidable in the axial direction, i.e. in the direction of thelongitudinal axis 5, and is spring-loaded (not shown).

The front part 25 of the smaller diameter section 13 of the sleeve 10,which is to be pressed, is inserted in a shaping tool 20, which has apipe-shaped body 21, which has several press jaws 22 a to 22 f, as shownin FIG. 2.

The pipe-shaped body 21 is—as shown in FIG. 2—provided with a total ofsix longitudinal slots or slits 23 distributed over its circumference,whereby six pipe segments or press jaws 22 a to 22 f are formed, whichhave tapering sections 22 a′ to 22 f′ on their free ends. The press jaws22 a to 22 f are arranged spring-loaded in the pipe-shaped body 21 andcan move in a radial direction. The press jaws 22 a-22 f taken togetherin the region of the tapering sections 22 a′ to 22 f′ have a truncatedcone-shaped or conical outer contour, wherein the conical outer surface24 cooperates with a counter ring 26 shown in FIG. 1.

The counter ring 26 likewise has a conical inner surface 27, whichslides over the outer surface 24 of the press jaws 22 a to 22 f duringaxial motion of the counter ring 26 over the shaping tool 20. Thecontacting surfaces of the counter ring 26 and the press jaws 22 a to 22f can be provided with a lubricating coating.

The counter ring 26 has a cylindrical section with a cylindricalinterior surface 28, which assists in the axial guiding of the shapingtool 20. The press jaws are moved in a radial direction by the axialmotion of the counter ring 16 over the shaping tool 20, whereby thesleeve 10 is pressed on the optical fiber bundle end 3.

The apparatus is provided with a heating jacket 30 in the embodimentshown in FIG. 1, which bears on the outer side of the counter ring 26.

In FIG. 3 a front view of another embodiment of the shaping tool 20 isshown. In this embodiment each press jaw 22 a to 22 f has its ownheating cartridge 31.

A detailed perspective view of the front end of a optical fiber bundle 1with a sleeve 10 is shown in FIG. 4. A shaping of the inner surface ofthe sleeve 10 occurs due to the pressing of the sleeve 10 on the opticalfibers 4, so that the outer optical fibers 4′ are pressed into thematerial of the sleeve 10 and are partially embedded in the material ofthe sleeve 10. Because of that a stable connection between the outeroptical fibers 4′ and the sleeve material is guaranteed, whereby thepull-out force is considerably increased. The optical fibers 4, 4′ aredeformed in this pressing process, in which no melting of the opticalfibers 4 occurs. However the optical fibers adhere in the sleeve and toeach other in all cases.

The disclosure in German Patent Application 10 2004 028 310.9-51 of Jun.12, 2004 is incorporated here by reference. This German PatentApplication describes the invention described and claimed in theappended claims and provides basis for a claim of priority for theinstant invention under 35 U.S.C. 119.

While the invention has been illustrated and described as embodied in amethod and apparatus for making an end of an optical fiber bundle and animproved optical fiber bundle made with same, it is not intended to belimited to the details shown, since various modifications and changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.What is claimed in the following appended claims is new.

PARTS LIST

-   1 optical fiber bundle-   2 protective sheathing-   3 end section-   4 optical fiber-   4′ outer optical fiber-   5 longitudinal axis-   10 sleeve-   11 collar-   12 larger diameter section-   13 smaller diameter section-   20 shaping tool-   21 pipe-shaped body-   22 a-22 f press jaws-   22 a′-22 f′ tapering section-   23 longitudinal slot or slit-   24 conical outer surface-   25 front or pressed part-   26 counter ring-   27 conical inner surface-   28 cylindrical inner surface-   30 heating jacket-   31 heating cartridge-   40 holder

1. An apparatus for producing an end of an optical fiber bundle having ametallic sleeve (10), said apparatus comprising a holding device (40)for holding an end section (3) of an optical fiber bundle (1), a shapingtool (20) for pressing the metallic sleeve (10) against the end section(3) of the optical fiber bundle, and at least one heating unit; whereinthe shaping tool comprises more than two press jaws (22 a-22 f) forsubstantially surrounding or enclosing the metallic sleeve (10), saidpress jaws being movable in a radial direction and heatable by said atleast one heating unit; and wherein said at least one heating unitcomprises a respective heating cartridge (31) arranged in each of saidpress jaws (22 a-22 f).
 2. The apparatus as defined in claim 1, furthercomprising a counter ring (26) in which the press jaws (22 a-22 f)engage, and wherein the press jaws have an outer surface (24) bearing onan inner surface (27) of the counter ring, the counter ring (26) ismovable in an axial direction over the press jaws (22 a-22 f), and thepress jaws (22 a-22 f) are movable in a radial direction during motionof the counter ring (26) over the press jaws.
 3. The apparatus asdefined in claim 2, wherein said press jaws (22 a-22 f) have respectivetapering sections (22 a′-22 f′) that narrow in a direction toward freeends thereof and said respective tapering sections (22 a′-22 f′) of saidpress jaws (22 a-22 f) together form a truncated conical shaped ortruncated pyramidal shaped outer surface.
 4. The apparatus as defined inclaim 2, wherein said outer surface (24) of said press jaws (22 a-22 f)and/or said inner surface (27) of the counter ring (26) are providedwith a lubricating coating.
 5. The apparatus as defined in claim 2,wherein said press jaws (22 a-22 f) are spring-loaded and are movableradially inwardly against a radially outwardly directed spring force, sothat the press jaws move back to an initial open position after pressingthe metallic sleeve against the end section.
 6. The apparatus as definedin claim 1, wherein the shaping tool (20) has a pipe-shaped body (21)with an end section and said end section of the pipe-shaped body (21) isprovided with a plurality of longitudinal slots (23) forming pipesegments separated by the longitudinal slots (23), said pipe segmentsacting as the press jaws (22 a-22 f).
 7. The apparatus as defined inclaim 1, wherein said holding device (40) is movable in an axialdirection and in relation to said shaping tool (20) so that the end ofthe optical fiber bundle provided with the metallic sleeve (10) can beinserted in said shaping tool (20) and outer optical fibers (4′) of saidoptical fiber bundle (1) can be embedded in material of the metallicsleeve (10) by said press jaws.
 8. An apparatus for producing an end ofan optical fiber bundle having a metallic sleeve (10), said apparatuscomprising a holding device (40) for holding an end section (3) of anoptical fiber bundle (1), a shaping tool (20) for pressing the metallicsleeve (10) against the end section (3) of the optical fiber bundle, andat least one heating unit; wherein the shaping tool comprises more thantwo press jaws (22 a-22 f) for substantially surrounding or enclosingthe metallic sleeve (10) and a counter ring (26) in which the press jaws(22 a-22 f) engage, said press jaws being movable in a radial directionand heatable by said at least one heating unit; and wherein said atleast one heating unit comprises a heating jacket (30) bearing on anouter surface of said counter ring (26) in which said press jaws (22 a22 f) engage.
 9. The apparatus as defined in claim 8, wherein said pressjaws have an outer surface (24) bearing on an inner surface (27) of thecounter ring and the counter ring (26), the counter ring (26) is movablein an axial direction over the press jaws (22 a-22 f), and the pressjaws (22 a-22 f) are movable in a radial direction during motion of thecounter ring (26) over the press jaws.
 10. The apparatus as defined inclaim 9, wherein said press jaws (22 a-22 f) have respective taperingsections (22 a′-22 f′) that narrow in a direction toward free endsthereof and said respective tapering sections (22 a′-22 f′) of saidpress jaws (22 a-22 f) together form a truncated conical shaped ortruncated pyramidal shaped outer surface.
 11. The apparatus as definedin claim 9, wherein said outer surface (24) of said press jaws (22 a-22f) and/or said inner surface (27) of the counter ring (26) are providedwith a lubricating coating.
 12. The apparatus as defined in claim 9,wherein said press jaws (22 a-22 f) are spring-loaded and are movableradially inwardly against a radially outwardly directed spring force, sothat the press jaws move back to an initial open position after pressingthe metallic sleeve against the end section.
 13. The apparatus asdefined in claim 8, wherein the shaping tool (20) has a pipe-shaped body(21) with an end section and said end section of the pipe-shaped body(21) is provided with a plurality of longitudinal slots (23) formingpipe segments separated by the longitudinal slots (23), said pipesegments acting as the press jaws (22 a-22 f).
 14. The apparatus asdefined in claim 8, wherein said holding device (40) is movable in anaxial direction and in relation to said shaping tool (20) so that theend of the optical fiber bundle provided with the metallic sleeve (10)can be inserted in said shaping tool (20) and outer optical fibers (4′)of said optical fiber bundle (1) can be embedded in material of themetallic sleeve (10) by said press jaws.